"Anything happening tonight?"

Has worked very well in getting an initial response from whomever I text, regardless of background. I like how it doesn't ask the recipient what she's doing, but only where she thinks the action is going to be tonight. If they are doing something fun that night, you're now in a great position to meet-up with them later or make plans on the spot (depending on the relationship). If they say "Nothing/Not Sure/What Have You Heard" you have an easy way to make plans right there.

Funny, I didn't think such a simple little thing could be such a good way to make plans with someone.